Question

Quaternary structure is found in
a. Simple monomeric proteins
b. Conjugated monomeric proteins
c. Oligo Proteins
d. Both B and C

Answer 1

Some proteins contain two or separate polypeptide chains or sub-units. Quaternary structure of proteins describes the way by which two or more polypeptide chains are joined to form an ordered biologically active protein.

Complete answer:
All the basic functions of life depend upon specific proteins. The proteins are big molecules built up from several smaller units. Backbone of all protein molecules is made up of linear chains of polypeptides. These polypeptides are made up of amino acids. The different levels of protein structures are- primary, secondary, tertiary and quaternary structure.
The primary structure is the arrangement of amino acids in a polypeptide chain.
The long peptide chains of proteins are folded into the relatively rigid confirmation called the secondary structure of protein. The tertiary structure of protein refers to the three dimensional structure.

The quaternary structure of proteins describes the way in which two or more polypeptide chains are packed together to form the overall structure of protein. Quaternary structure is found in oligo proteins because it consists of two or more polypeptide chains that are linked together by chemical interactions like hydrophobic interactions or electrostatic structure. For example, haemoglobin is an oligo protein as it consists of two alpha and two beta chains.
Simple monomeric proteins are defined as those proteins that upon hydrolysis yield only amino acids or their derivatives. Example: albumins and globulins etc.

Conjugated monomeric proteins are composed of simple protein combined with some nonprotein (prosthetic part) substances. Example: nuclein and mycin etc.

Hence, the correct answer is option (C).

Note: Quaternary structure of the protein is made up of two or more separate polypeptide chains or sub-units, which may be identical or different in structure, Two or more polypeptide combines to form multimers.